Emergency Services crews were called to the scene of a crash involving a truck between Raurimu Rd and Manson Siding near National Park.
Crews were notified around 9.25am.
A police spokeswoman confirmed the road had become blocked due to the crash.
A St Johns spokeswoman confirmed they sent one ambulance and a rescue helicopter that transported a person to Waikato Hospital in a serious condition.
Emergency crews also received a report around 9.10am of a car colliding with a barrier at the intersection of State Highways 48 and 47 at Tongariro Forest Park.
The St Johns spokeswoman confirmed they sent one ambulance and another rescue helicopter that transported one person to Waikato Hospital in a serious condition.
At 6.10am this morning police were alerted to a car having slid off the road and into a ditch at or near the intersection of Hururua Rd and SH4.
The driver appeared to be uninjured and advised he did not need roadside assistance.
At the same time, police were alerted to a truck that had rolled blocking the southbound lane on State Highway 4, 1.5km north of Ohutu Rd.
The road is still closed from Whanganui through to Tohunga Junction so the truck and trailer could be removed.